Lubricating compositions



3,041,284 LUBRICATING CUMPDSITIONS George M. Calhoun, Berkeley, andWilliam A. Hewett,

Oil Company, a

This invention relates to lubricants, particularly those useful forlubrication under severe operating conditions, such as those underextreme high speed and at high temperatures.

It is well known that the high pressure occurring in certain types ofgears and bearings may cause rupture of lubricant films with consequentdamage to the machinery. It is known that various base lubricants can beimproved in their protective properties for rubbing surfaces by theaddition of certain substances, so-called extreme pressure agents, sothat excessive wear, scufiing and seizure which normally follow a breakin the film lubricant are minimized or prevented.

It is known that certain compounds of metal-reactive elements, such ascertain compounds of chlorine, sulfur and phosphorus, as well as certainother compounds, such as some compounds of lead, impart extreme pressureproperties to various lubricants. Notable among the substancesheretofore used are the lead soaps, phosphoric acid esters, free orbound sulfur and certain chlorinated organic compounds. A principalobjection to many of these extreme pressure agents is their generallyhigh reactivity with the metallic surface, causing etching, corrosionand discoloration of the metal surface. Another objection to chemicallyreactive extreme pressure agents is that they alter the originalchemical nature of the contacting surface, which under certainconditions is undesirable. Additionally, because of the activity ofagents of this type, they usually are depleted rapidly resulting in onlya temporary solution to the problem of extreme pressure lubrication.

It has now been discovered that improved extreme pressure lubricants areprovided by a suitable lubricating oil containing an oil-solublethiaether containing at least two oxygen-containing radicals or groupsand in which at least one of any such thiaether sulfur atom is separatedfrom one of the polar groups by a chain of from 1 to 4 carbon atoms andfrom any other polar group by a chain of at least 7 carbon atoms. Thethiaethers are mercapto modified ethylenically unsaturated higheraliphatic (cyclic or acylic) compounds containing oxygen-containingradical or polar group, wherein such polar group is either a terminal oran internal group and is an alcohol (OH), ether (O), acid (COOH) orester (-COOC'- functional group. At least one thiaether sulfur isassociated with one of the polar group in a radical represented by -S(CH-X where X is OR or COOR', and the Rs being hydrogen or C alkyl radicaland n is an integer of from 1 to 4, preferably 1. The number of S('CI-IX units in the final compound depends on the degree of unsaturation ofthe unsaturated aliphatic polar compound and generally varies from 1 to4, preferably from 1 to 2. Compounds of this type can be represented bythe formula where R is an oil-solubilizing hydrocarbyl radical,preferably C alkyl radical, R" is an alkyl radical, preferably of atleast 7 carbon atoms, Y is an oxygen-containing radical such as alcohol,acid, ether or ester group, and in the case of the latter two anadditional R radical is present, X and n are the same as defined above.

3,@4l,284 Patented June 26, 1962 Compounds of the type under discussioncan be prepared by reacting a mercapto compound with an unsaturated acidor other equivalent compound. The mercapto compounds include themercapto aliphatic carboxylic acids such as mercapto acetic acid,mercapto propionic acid, mercapto butyric, or mercapto-alkanols such asZ-mercaptoethanol, 2- and 3-mercaptopropanol, 2-, 3- and 4-mercaptobutanol, or ethers of said mercaptoalcohols such as methyl oroctyl Z-mercaptoethanyl or mercapto esters, e.g., ethyl mercapto acetateor ethyl mercaptobutylate, and mixtures thereof. The unsaturatedlong-chain polar containing compounds which are reacted with themercapto compound may be a long-chain unsaturated fatty acid, e.g.,oleic acid, linoleic acid, linolenic acid, erucic acid, ricinoleic acidor an unsaturated fatty alcohol, e.g., oleyl alcohol, ricinoleylalcohol, etc., or unsaturated esters'in which either the fatty acid oralcohol can be unsaturated or where both the acid and alcohol portion ofthe ester are unsaturated, e.g., methyl oleate, ethyl oleate, oleylstearate, oleyl nndecenoate, lauryl oleate, glycerol trioleate, vinyloleate, oleyl oleate, or the like.

The additives can be prepared by the methods described by Koenig et al.JACS 79, 362 (1957) or Fitzgerald Jr. Org. Chem. 22, 197 (1957) andpreferably at low temperatures, from room temperature to about 50 C. andin the presence of a free radical catalyst such as azo or peroxidecatalysts or ultraviolet light and a non-reactive solvent such asbenzene, toluene, xylene, or the like. Suitable initiators includevarious free radical-yielding, heterocyclic and alicyclic peroxides,such as diethyl peroxide, tertiary butyl hydroperoxide, dibenzoylperoxide, ditertbutyl peroxide, dimethylthienyl peroxide, dicyclohexylperoxide, dilauroyl peroxide and urea peroxide. These are mentioned byway of non-limiting examples of suitable organic peroxides. Otherinitiating compounds known include emulsion redox systems, such as amixture of sodium bisulfite and persulfate, ammonium persulfate, alkalimetal perborates, azo compounds, such asalpha,alpha-azodiisobutylronitrile, etc.

The following examples illustrate the preparation of suitable additivesfor use in accordance with the present invention.

EXAMPLE I About 600 grams of oleic acid and 223.5 grams ofmercaptoacetic acid were mixed in a flask at 20-25 C. About 240 drops(30 drops at a time) of t-butyl hydroperoxide were added over a periodof 2 hours and the temperature was kept at about 37 C. The reaction mix.

Percent H Percent Percent Percent Eq, 0 O Wt.

EXAMPLE 11 About 600 grams of ethyl oleate and 223.5 grams ofmercaptoacetic acid were mixed in a flask at 20-25 C. About 240 (30drops at a time) of t butyl hydroperoxide were added over a period of 2hours and the temperature was kept at about 37 C. The reaction mixturewas diluted with 2 volumes of diethyl ether, washed with 12 liters ofwater to pH 4, dried over Na SO filtered and the solvent stripped at C.and 2 mm. pressure. The

final product was a mixture of ethyl 9- andIO-carboxymethylmercaptostearate which analyzed as follows:

Percent Percent Percent Percent Eq. C H O Wt.

Found 65.7 10.5 16.0 7. 75 472 Theory 65.6 m5 15. 9 7.97 402 EXAMPLE HIAbout 600 grams of n'cinoleic acid and 223.5 grams of mercaptoaceticacid were mixed in a flask at 20-25", C. About 240 drops (30 drops at atime) of t-butyl hydroperoxide were added over a period of 2 hours andthe temperature was kept at about 27 C. The reaction mixture was dilutedwith 2 volumes of diethyl ether, washed with 12 liters of water to pH 4,dried over Na SO filtered and the solvent stripped at 155 C. and 2 mm.pressure. The final product was a mixture of 9- and10-carboxymcthylmercapto-l2-hydroxystearic acid with a deter-minedequivalent weight of 207 (theory 195).

EXAMPLE IV About 600 grams of glyceryl trioleate and 223.5 grams ofmercaptoacetic acid were mixed in a flask at 20-25 C. About 240 drops(30 drops at a time) of t-butyl hydroperoxide were added over a periodof 2 hours and the temperature was kept at about 37 C. The reactionmixture was diluted with 2 volumes of diethyl ether, washed with 12liters of water to pH 4, dried over Na SO filtered and the solventstripped at 155 C. and 2 mm. pressure. The final product was a mixtureof glyceryl tris(9- and 10-carboxymethylmercapto'stearate) with adetermined equivalent weight of 445 (theory 387).

. EXAMPLE v EXAMPLE VI About 600 grams of oleyl oleate and 223.5 gramsof mercaptoacetic acid were mixed in a flask at 20.25 C. About 240 (30drops at a time) of t-butyl hydroperoxide were added over a period of 2hours and the temperature was kept at about 37 C. The reaction mixturewas diluted with 2 volumes of diethyl ether, washed with 12 liters ofwater to pH 4, dried over Na SO filtered and the solvent stripped at 155C. and 2 mm. pressure. The final product was a mixture of 9 andIO-carboxymethylmercaptostearyl 9- and 10-carboxymethylmercaptostearate.The compound was completely oil soluble.

Following the above procedures the following additional compounds wereprepared:

EXAMPLE VII 9- and l0-[2-hydroxyethylmercapto]stearoyD-S-hydroxyl-3-thiavaleric acid.

' EXAMPLE VIII 9- and 10-(Z-hydroxyethylmercapto)-3-thiaheneicosanoicacid.

EXAMPLE IX -hydroxy-3-thiamyl 9- and IO-carboxymethylmercaptostearate.

EXAMPLE X 9- and -carbomethylmercaptostearyl-(2-hydroxyethylmerc apto)-undeceno ate.-

The cercapto-modified acids, alcohols, esters, etc., in general, areoil-soluble and can be used in amounts of from about 0.5% to about 20%,preferably from about 1% to about 5% by weight. With certain oils themercapto-rnodified acids or alcohols form opaque solutions, but they canbe rendered transparent by addition of a small amount (01-10%) of anoil-soluble branchedchain aliphatic monohydric alcohol, oil-soluble highmolecular weight fatty acid or monoester of said fatty acid andpolyhydric alcohols. The alcohols, fatty acids or monoesters effectivelyclarify oils containing mercapto acids or alcohols as described withoutdestroying the extreme pressure properties of such oil compositions. Themercapto-modified unsaturated esters as described in Example VI formclear transparent oil compositions and generally do not require anyclarifiers.

Oil-soluble alkanols which are particularly useful as clarifiers are theso-called OX0 alcohols of 3 to 5 carbon atoms, and copolymers ofmixtures of such alkenes, by catalyzed reaction with carbon monoxide andhydrogen in accordance with the conditions of the OX0 process, as iswell known in the art. The composition of a typical C OXO-alcoholmixture derived from a mixture of C -olefins, produced by polymerizationof a typical olefin refinery cracked gas fraction of C -C hydrocarbonsgiven in Table I.

TABLE I Alcohol: Percent, wt. I

' 3,5-dimethyl hexanol 29 4,5-dimethyl hexanol 25 3,4-dimethyl hexanol17 S-methylheptanol; 3-methy1 heptanol l6 S-ethyl hexanol 2.35,5-dimethyl hexanol 1.4 Alpha-alkyl alkanols 4.3 Others 5.0

Other suitable alkanols include 6-methyl-l-heptano1,2-npropyl-l-pentanol, 3-n-propyl-1-hexanol, 2,2-dimcthyl-loctanol,10,IO-di-mcthyl-l-undecanol, 3-isopropyl-l-heptanol and the mixturesthereof.

Fatty acids useful as clarifiers include the saturated and unsaturatedoil-soluble fatty acids having from 10 to 30 carbon atoms such ascapric, lauric, oleic, linol'eic, ricinoleic acids and mixtures thereof.

Monoesters derived from simple alkane polyols and long chain fatty acidswhich are useful as clarifiers include oil-soluble glycerol monooleate,glycerol monostearate, glycerol monoricinoleate, pentaerythritol monoanddilaurate, pentaerythritol monoand dioleate, pentaerythritol monoanddistearate, mono-, di-, and triethylene glycol monoleate, propyleneglycol monoricinoleate, triethylene glycol monostearate, sorbitolmonolaurate, man- 7 nitol monooleate, mannitol dioleate, sorbitoldioleate, etc.

Lubricating oils useful for the preparation of compositions of thisinvention can be one or more of a variety of synthetic oils or naturalhydrocarbon oils having a viscosity range of from SUS at 100 F. to 250SUS at 210 (SAE viscosity number ranging from SAE 5 to SAE 90). Thenatural hydrocarbon oils can be obtained from paraffinic naphthenic,asphaltic or mixed base crudes,

and/or mixtures thereof. Synthetic oils include polymerized olefins,alkylated aromatics, isomerized waxes, copolymers of alkylene glycolsand alkylene oxide (Ucon fluids) which are described in US. Patents2,425,755,

2,425,845 and 2,774,733 such as Ucon 50HB170, Ucon 50HB660 or UconLB550X and which are copolymers of ethylene and LIZ-propylene oxides,the monoand diols, as well as their ether derivatives; organic esters ofaliphatic dibasic acids such as di-Z-ethylhexyl sebacate ordi-Z-ethylhexyl adipate and the like. The hydrocarbon oils may beblended with fixed oils such as castor oil, lard oil and the like and/or synthetic oils as mentioned or silicone polymers and the like.Typical oils of this type include petroleum motor oils which are (A)paraffinic in character and (B) naphthenic in character having thefollowing properties:

(A) (SAE W) (SAE 30) Pour point, F 10 5 Flash, F 300 415 Viscosity, SUSat 210 F 44 58 Viscosity Index 90 60 Other suitable Oils are the gasturbine lube oils having the following properties:

The following compositions are illustrative of the invention, thepercentages being by Weight:

Composition A Example I additive 2%. 1010 Mineral oil Balance.

Composition B Example I additive 2%. Glycerol monoleate 2%. 1010 Mineraloil Balance.

Composition C Example III additive 2%. Glycerol monoleate 8%. 1010Mineral oil Balance.

Composition D Example IV additive 2%. Glycerol monooleate 5%. 1010Mineral oil Balance.

I Composition E Example II additive 2%. 1010 Mineral oil Balance.

Composition F Example V additive 2%. C H OH (made by OXO process) 3.5%.1010 Mineral oil Balance.

Composition G Example I additive 2%. Laurie acid 2%. SAE 90 Mineral oilBalance.

Composition H Example I additive 2%. C13H27OH (made by OXO process)2.74%. SAE 90 Mineral oil Balance.

Composition I Example I additive 5%.

Ucon 50HB660 (polyethylene-propylene glycol having a SUS at 100 F. of660)---- Balance.

Composition J Example I additive 2%. Di-2-ethylhexyl sebacate Balance.

Composition K Example VI additive 2%. 1010 Mineral lubricating oilBalance.

Composition L Example VI additive 5 Ucon 50HB660 fluid Balance.

'6 Composition M Example VI additive 2.5%. Mineral lubricating oil (SAEBalance.

Composition 0 Example X 2%. C13H27OH (made by OXO process) 2.5 1010Mineral oil Balance.

Composition P Example IX 2%. 1010 Mineral oil Balance.

Composition Q Example VII 2.5%. 1010 Mineral oil Balance.

Compositions of this invention were evaluated for their extreme pressureproperties on a Spur-Gear machine. The machine consists essentially oftwo geometrically similar pairs of gears connected by two parallelshafts. The gear pairs are placed in separate gear boxes, which alsocontain the supporting ball bearings. One of the shafts consists of twosections connected by a coupling. Loading is accomplished by locking oneside of the coupling and applying torque to the other. The conditions ofthe test were:

Speed3200 and 10,000 r.p.m.

Oil temperature-38 C. and C. Oil flow-rate-l0 cc./scc.

Load in increments 5 min. at each setting TABLE II Composition: ScoreLoad, lbs/in.

A 12,700 (3200 r.p.m.). B 9,900 10,000 r.p.m.). C 9,900 (10,000 r.p.m.).D 9,900 (10,000 r.p.m.). E 7,800 (3,200 r.p.m.). F 12,000 (3,200r.p.m.). K 7,800 (3,200 rpm.

at 160 C.). O 9,200 (10,000 r.p.m.). P 8,500 (10,000 r.p.m.). Q 7,100(10,000 r.p.m.). 1010 Mineral oil+2% alkenyl succinic acid 1,400 (3,200r.p.m.). 1010 Mineral oil+2% malonic acid 2,800 (3,200 r.p.m.). 1010Mineral oil+2% 3- hcxadecyl adipic acid 1,400 (3,200 r.p.m.). 1010Mineral oil+2% thiodiglycolic acid 5,000 (3,200 r.p.m.). 1010 Mineraloil+2% thio-alpha,alpha'- I bis (stearic acid) 3,500 (3,200 r.p.m.).1010 Mineral oil+2% dodecyl-mercapto succinic acid 1,400 10,000 r.p.m.).1010 Mineral oil+2% heptylmercapto succinic acid 4,200 (3,200 r.p.m.).1010 Mineral oil+2% alpha mercapto benzoic [acid 4,200 (3,200 r.p.m.).1010 Mineral oi1+10% glycerol monooleate 1,800 (3,200 r.p.m.). 1010Mineral oil+13.25%

lauric acid 3,400 (3,200 r.p.m.).

1010 Mineral oi1+2% C13H2I7OH (OXO process) 600 (3,200 r.p.m.).

1010 Mineral oil 600 (3,200 r.p.m.).

The data show the outstanding enhancement of the load-carrying abilityof the oil effected by the mercaptocontaining acids of the invention, asrepresented by those of Compositions A through F, K, O, P and Q. 'On theother hand, malonic acid, succinic acid, 3-hexadecyl adipic acid and C-alkenyl succinic acid as well as sulfur-containing acids outside thescope used by applicants such as thiodiglycolic acid,thio-alpha,alpha'-bis(stearic acid),

dodecyl-mercapto-succinic acid, heptylmercapto-succinic acid,alpha-mercaptobenzoic acid, glycerol-monooleate, lauric acid or OXalcohol efiected only a slight improvement.

Compositions of the present invention were also tested for theircorrosion and sludge resistant properties by the following methods: (1)a Timken 2126 steel hearing was immersed in a test composition andplaced in an open air oven at 150 C. for 65 hours, and at the end of thetest, the bearing examined and (2) steel rods (3/16 by 3") Were immersedin test compositions for 21 /2 hours at 150 C. and the amount of sludgeformed on the rods was noted as shown in Table III.

The sulfur-containing compounds of this invention are useful also forproviding superior load-carrying properties for lubricating oils whichcontain minor amounts of other agents which are non-reactive with thedicarboxylic acids, such as silicone anti-foaming. agents, alkylphenolanti-oxidants, polyacrylate ester viscosity-index improvers, and thelike.

This application is a continuation-in-part of our copending patentapplication Serial No. 699,919, filed- December 2, 1957, and which hasmatured as US. Patent 2,- 994,662 on August 1, 1961. r

We claim as our invention:

1. A lubricating oil composition comprising a major amount of minerallubricating oil and from about 0.5% to about 20% of an oil-solublepolythiaether having the wherein R is an oil-solubilizing alkyl radicalof 8-30 carbon atoms, R is an alkyl radical of at least 7-10 carbonatoms, Y is an ester radical, and X is an oxygen-containing radicalselected from the group consisting of -OH and -COOH, n is an integer offrom 1 to 4 and one S(CH ),,X group being separated from Y by a carbonchain of from 7 to 10 carbon atoms.

2. A mineral lubricating oil composition comprising a major amount ofmineral lubricating oil and from about 1% to about 5% of a di(carboxy Calkyl mercapto) substituted long-chain fatty acid ester, one of saidcarboxy C alkyl mercapto radicals being from 7 to 10 carbon atoms awayfrom. the carboxyl radical of the ester.

3. A mineral lubricating oil composition comprising a major amount ofmineral lubricating oil and from about 1% to about 5% of a di(hydroxy Calkyl mercapto) substituted long-chain fatty acid ester, one of saidhydroXy C alkyl mercapto radicals being from 7 to 10 carbon atoms awayfrom the carboxyl radical of the ester.

4. The lubricating oil composition of claim 1 containing from about 0.1%to about 10% of glycerol monooleate.

5. The lubricating oil composition of claim 1 containing from about 0.1%to about 10% of lauric acid.

6. The lubricating oil composition of claim 1 containing from about 0.1%to about 10% of an oil-soluble branched-chain Oxo alcohol.

7. The lubricating oil composition of claim 2 containing from about 0.1%to about 10% of glycerol monooleate.

8. The lubricating oil composition of claim 3 containing from about 0.1%to about 10% of an oil-soluble branched-chain OX0 alcohol.

formula References Cited in the file of this patent UNITED STATESPATENTS 2,317,666 Burwell et al. Apr. 27, 1943 2,449,996 Gresham et alSept. 28, 1948 2,644,793 Rudel et al. July 7, 1953 2,649,416 Richter etal Aug. 18, 1953 2,737,525 Mulvaney Mar. 6, 1956 2,884,379 Rudelet a1.Apr. 28, 1959 2,892,852 Koenig et al. June 30, 1959 FOREIGN PATENTS701,993 Great Britain Ian. 6, 1954

1. A LUBRICATING OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF MINERALLUBRICATING OIL AND FROM ABOUT 0.5% TO ABOUT 20% OF AN OIL-SOLUBLEPOLYTHIAETHER HAVING THE FORMULA